(Aneta Kielar/University of Arizona)

A person with primary progressive aphasia activates part of the right-hand side of their brain (shown in blue) to decipher a sentence, whereas the normal person (left-hand image) does not.

A team of researchers at University of Arizona and the University of Toronto have published a study of a rare dementia called primary progressive aphasia, or PPA.

The research, which appeared last month in the journal NeuroImage: Clinical, linked improved patient outcomes to the brain's capacity to "recruit" other areas of the brain to make up for their deficits.

Neuron loss in the brain's language areas causes people with PPA to lose their ability to comprehend or use speech.

"It's different from other dementias in that its first symptom is language difficulty. In other dementias, usually the symptoms are mental, some sort of behavioral symptoms, changes in personality," said lead author Aneta Kielar, an assistant professor in speech and hearing sciences at UA.

Yet some PPA patients function much better than others. To learn why, researchers noted subjects' responses to syntax errors or word errors.

For example, "He will go to the library and check out a stack of puppies," contains a word error, whereas "He will going to the library and check out a stack of books," is syntactically incorrect.

The scientists then used a special liquid-helium-cooled helmet to map magnetic fields created by neurons firing in subject's brains as they evaluated the sentences.

Previous electrophysiological work has focused mainly on language processing at the single-word level.

Kielar said she and her colleagues saw better responses from patients whose brains had "rewired" themselves to compensate for neural damage. This involved employing neurons in the right hemisphere temporoparietal region, which generally assists in social and attention-related tasks.

"Patients who did better on the task — who were more accurate on the task — they recruited right hemisphere regions to process language."

The findings could point to new therapies for PPA and other neurolinguistic disorders like stroke aphasia, which Kielar is currently studying.

"Right now, there is no treatment for dementia, which is unfortunate, and there's no treatment for PPA. But, by knowing which regions of the brain are affected by this disorder, and what brain functions, we can work on targeting those regions with different types of treatments that will maybe slow down this disorder."